Chemo treats cancer better with fasting, paper finds

A recent paper says fasting and chemotherapy, used together, can fight cancer better.

By Tom Valeo, Times Correspondent

Published July 22 2014

Updated July 22 2014

The history of cancer treatment includes a long list of quack diets claiming patients can eat their way back to good health, but one approach, which involves eating less and minimizing carbohydrates, appears to produce genuine benefits.

For the past decade, Dr. Valter Longo, director of the Longevity Institute of the University of Southern California, has been studying the effects of calorie restriction on diseases associated with aging, including cancer.

In a paper recently published in the journal Cell Stem Cell, Longo and his colleagues report that periodic fasting in mice helped reduce the immune system decline caused by chemotherapy and aging.

The researchers also analyzed data from a clinical trial involving human cancer patients and found that those who fasted for 72 hours when receiving chemotherapy showed normal numbers of the white blood cells needed to maintain robust functioning of the immune system.

Three clinical trials are being done at USC's Norris Comprehensive Cancer Center to test the effect of periodic fasting. In one trial, cancer patients are divided into groups and follow various fasting regimens. Some patients, for example, fast for two days before chemo, and one day after, while others fast for four days but are allowed a few hundred calories a day of soups and other low-carb foods.

"That's much easier for patients to do," Longo said.

The goal is to put the patients in a ketogenic state in which the body burns fat rather than carbohydrates and sugar. "It's not what people refer to as a ketogenic diet, which is based on eating either a high-fat or a high-fat, high-protein diet," Longo said. "We've done that and it just doesn't work. This is a low-protein, low-carb diet."

Patients who fast still experience a drop in white blood cells after chemotherapy, but the cells rebound quickly when the patients start to eat again, according to the Cell Stem Cell paper.

In other research, Longo and his colleagues have demonstrated that fasting cycles are as effective as chemotherapy at slowing cancer progression in mice. "The fasting made the chemo work better," Longo said. "With chemo alone, you almost never get a cure, and with fasting alone, you almost never get a cure, but with chemo plus fasting, 20 to 60 percent of the animals become cancer free. I think the potential is there to do the same for people"

Longo cautions cancer patients against trying to fast on their own. "When people improvise, they tend to do things that could hurt them," he said. "People can have a major drop in blood pressure and glucose levels. If they are diabetic and insulin dependent, they could die."

Also, fasting causes weight loss, which can weaken cancer patients.

Nevertheless, his recent work suggests that cancer patients might benefit from fasting before and after chemotherapy because of the beneficial changes in metabolism that take place in the body when faced with a shortage of food.

"This effect, which may have evolved to reduce energy expenditure during periods of starvation," Longo said, "is able to switch stem cells to a mode in which they not only regenerate immune cells and reverse the immunosuppression caused by chemotherapy, but also rejuvenate the immune system of old mice."